The present invention provides a high dynamic range digital converter. More, particularly, the present invention provides a variable gain digital converter system which is suitable for digitizing signals that have high dynamic range such as signals in photon detection systems or other various applications.
In general, there are problems in digitizing a signal having a high dynamic range. First, the range of signals levels over a high dynamic range signal can saturate the analog-to-digital converter and/or the amplifier in the receiver stage of the photon detection system. In the past, known photon detection systems typically amplify such signal prior to analog-to-digital conversion in order to improve the signal to noise (S/N) ratio. Secondly, to cover the typical high dynamic range of the photon detection system, at least four or more 16-bit analog-to-digital converters are required per amplifier, which is very costly. The use of a single 20-bit A/D converter to cover the high dynamic range adds substantial cost, complexity, and is typically too slow to be effective. In addition, the use of multiple analog-to-digital converters requires processing multiple signals to determine which converter is in range, thereby increasing system complexity and making it more difficult to calibrate.
Accordingly, what is required is a single analog-to-digital converter system which is capable of converting an input signal having a high dynamic range into a digital signal which consumes less time and is cost effective.
The present invention provides a single analog-to-digital converter which is capable of converting an input signal having a high dynamic range into a digital signal which is within the range of the analog-to-digital converter. Additionally, the present invention provides an analog-to-digital converter which is capable of converting an input signal having a high dynamic range into a digital signal by controlling the amplification of the signal to achieve the optimal gain that falls within the range of the analog-to-digital converter.
In accordance with one embodiment of the present invention, there is provided an apparatus for amplifying signals of high dynamic range having an amplifier bank where the amplifier bank has an input for receiving an analog signal and having a plurality of channels, where each channel includes an output for producing an amplified signal corresponding to the analog signal; a switch coupled to the output of the amplifier bank and having a switch output and producing at the switch output one of the amplified signal; a comparator bank including an output port and having an input coupled to the outputs of the channels in the amplifier bank and to reference voltage signals; a microprocessor coupled to the switch and to the output port of the comparator bank for controlling the switch to select one of the amplified signal; and an analog-to-digital converter having an analog input coupled to the switch output for receiving the amplified signal and including a data output port, and converting the selected amplified signal into a digital signal for output at the data output port.
In accordance with the second embodiment of the present invention, there is provided a high dynamic range digital converter system having a first programmable variable amplifier, where the first programmable variable amplifier includes a first input and first output; and for receiving an input voltage signal at the first input and producing a first attenuated voltage signal at the first output, wherein the first attenuated voltage signal represents first gain of the first programmable variable amplifier; a second programmable variable amplifier having a second output and second input, the second input being coupled to the first output of the first programmable variable amplifier for receiving the first attenuated voltage signal and for producing a second attenuated voltage signal at the second output, said second attenuated voltage signal representing a second gain of the second programmable variable amplifier; an analog-to-digital converter having an output port and an input port, the input port being coupled to the second output of the second programmable variable amplifier and for converting the second attenuated voltage signal to a digital signal at the output port; and microprocessor coupled to the output port of the analog-to-digital converter for receiving the digital signal and the microprocessor coupled to the first and second programmable variable amplifiers for controlling the first and second gain.
In accordance with the third embodiment of the present invention, there is provided a high dynamic range digital converter system having a first programmable variable amplifier, where the first programmable variable amplifier has a first input and first output; and for receiving an input voltage signal at the first input and producing a first attenuated voltage signal at the first output, the first attenuated voltage signal representing a first gain of the first programmable variable amplifier; a second programmable variable amplifier having a second output and second input, the second input being coupled to the first output of the first programmable variable amplifier for receiving the first attenuated voltage signal and for producing a second attenuated voltage signal at the second output, the second attenuated voltage signal representing a second gain of the second programmable variable amplifier; a comparator bank including an output port and having an input port for receiving input voltage signal and reference voltage signals; a microprocessor coupled to the first and second programmable variable amplifiers and to the output port of the comparator bank for controlling the first and second programmable variable amplifiers to adjust the first and second gain; and an analog-to-digital converter having an output and input, the input being coupled to the second output of the second programmable variable amplifier, and for converting the second attenuated voltage signal to a digital signal based upon the adjusted first and second gain.